Numerous methods exist for delivering substances to desired locations in vivo or in vitro. One such method uses devices or objects that contain a substance and will release the substance within a desired location. One desirable application for such methods is the administration of such objects to a location within the body of an organism, followed by the subsequent release of the desired substance into the body. In these examples, the implant often contains the substance and a carrier. After implantation, the substance is released by a variety of means including, for example, diffusion from an implant or dissolution or other degradation of a capsule coat.
Biocompatibility is a desirable attribute in compositions designed for substance delivery. With surgical and subdermal implants, for example, the substance to be delivered is often contained in a matrix comprised of synthetic polymers. Where natural products are used in making bandages, the products typically comprise wood products such as cellulose or other materials that are not readily absorbed by the body of the recipient. Accordingly, such bandages must eventually be removed. Implants compressed from natural materials that may be absorbed by the body are one way to improve biocompatibility and is one area in which improvements are desired.
There is also a continuing need for greater versatility and flexibility in substance delivery technology. Additional techniques for controlling release kinetics and spatial patterns of release or delivery are examples of developments that can improve substance delivery. Implants in which there is refined control of structure at the microscopic or molecular level and overall implant shape are also desired. Such methods could allow, for example, further refinements in control of pore size or other attributes that affect diffusion in and out of a matrix, or more refined control of the distribution of a substance within a matrix. New methods that allow encapsulation of living cells within a matrix are especially desired. Such methods would allow implants to contain, for example, cells that produced desired substances, cells that promote tissue growth, or cells that serve both of these functions.
What is needed therefore are new compositions for use in drug delivery that provide additional and improved methods of controlling configuration of drug delivery systems. Compositions with improved biocompatibility compared to those currently used in substance delivery and/or that can contain living cells are also needed. What is further needed are new methods of substance delivery using such compositions. Finally, methods for making such compositions are also needed.